The fabrication of a semiconductor device involves a plurality of discrete and complex processes. Recently, there has been a transition to create three dimensional devices in the semiconductor industry. As the name suggests, these semiconductor devices have a length and width, but also have a height. To process these three dimensional devices, angled ion implants may be used.
Angled ion implants refer to those ion beams which strike the substrate at a non-zero angle. For consistency, an angle of 0° is defined as one in which the ion beam strikes the substrate at an angle perpendicular to the surface of the substrate. Angled ion beams have many applications. For example, they may be used to implant a sidewall of a fin structure or a trench. Angled ion beams may also be used for etching processes, deposition processes and other applications.
One way to perform these angled ion implants is to rotate or tilt the platen on which the substrate is disposed. In other words, the ion beam is generated in the traditional manner, but the platen is tilted so that the ion beam strikes the substrate at a non-zero angle. This approach may allow the generation of an ion beam which strikes the substrate at an angle of 20° or more.
One shortcoming with this approach is that the various regions of the substrate are at different distances from the ion beam source. For example, by tilting, several regions of the substrate will be closer to the ion beam source than other regions. This may cause process variations across the substrate.
Another approach is to rotate the ion beam source with respect to the substrate to achieve the desired angle of the extracted ion beam. This approach has similar shortcomings as the previously described method of tilting the substrate.
Another approach is to control and vary the shape of the plasma sheath to vary the angle of the ions extracted from a plasma processing chamber. However, this approach may have limitations in terms of the amount of current that may be extracted.
Therefore, it would be advantageous if there was a system for generating a high current, low energy angled ion beam that did not suffer from these limitations. Further, it would be beneficial if the angle used for the ion implant was highly adjustable and easy to manipulate.